There are many ways to fasten metal beams and brackets together and, of course, the most well-known are screws, bolts, rivets the like.
In many instances, however, it is not easy or effective to use such fasteners, and it is more economical to be able to form the fastening device out of the same material as the elements which are being fastened together.
In the manufacture and production of metal frames for buildings and particularly for doors or windows and the like, and in particular in heavy-duty installations, such as factories, farm buildings, etc., fairly heavy and large and thick channel beams are used, and many have a U-shaped cross-section.
In the production of large doors for aircraft hangers, farm barns, truck garages and the like, these channel members are often made of 14 gauge steel, which is 0.074" thick. A typical beam is 4" wide with legs 2" long and provides a heavy, rigid form-retaining member.
In the assembly of such doors, it is found to be particularly effective to fasten the members together using a tab which is formed in the leg or legs of one of the members, and which can be bent or inserted into an abutting or mating hole in another of the metal members.
A form of such a fastener is shown in U.S. Pat. Nos. 4,021,988 and 4,494,354. As practical as such devices have been in the past, they are ineffective because the slots are bigger than the tabs whereby the tabs and the slots do not fit closely together. In the manufacture thereof, the tolerances provide further discrepancies which, when the beams are assembled, do not pull them tightly, one to the other.
To overcome such problem, the tabs of prior devices had to be curled around the edge of the openings and crimped against the inner surface of the channel members. This was often difficult, if not impossible, and the result was that the members were not tightly connected.
It is an object of the present invention to provide a tab and slot arrangement for holding metal channel members together in such a way that the elements are held together rigidly and immovably in the longitudinal as well as the transverse direction.
Another object of the present invention is to provide an inexpensive means for securely inter-connecting U-shaped channel members.
Another object of the present invention is to provide a rigid fastening member for U-shaped channels which does not require the use of third elements such as screws, rivets, bolts and the like.
With the above and other objects in view, further information and a better understanding of the present invention may be achieved by referring to the following detailed description.